Some biopsy devices include a tubular cutting element or cannula having a body tissue cutting distal end, and a stylet slidable in the cannula and having a pointed distal end for piercing tissue and a cavity for receiving tissue to be sampled. In using such a device, the stylet and cannula are relatively positioned so that the distal end of the cannula covers the cavity and closely surrounds the distal end of the stylet to prevent the coring of tissue during insertion into the patient. In one method of using such a device, the stylet and cannula are inserted to a position either in the tissue from which a sample is to be taken or to a point adjacent such tissue. The cannula may then be held stationary with one hand, while the stylet is moved distally with the other hand so that the distal end and the cavity of the stylet move into tissue from which a sample is to be taken. Next, the stylet is held stationary with one hand while the cannula is moved distally thereby cutting tissue that has moved into the cavity. With the tissue sample within the cavity and covered by the cannula, the stylet and cannula are removed from the patient. The body tissue sample may then be removed from the biopsy device for testing purposes.
The above procedure is somewhat complicated and there is the danger of inadvertently moving the wrong member at the wrong time. Because the two members are at times movable together and other times movable relative to each other in performing the biopsy, the person performing the biopsy may inadvertently fail to use the proper sequence of movements or steps in effecting the above precedure. This can, in some cases, result in damage to the patient or failure to obtain a sample thereby requiring a second insertion.
With some biopsy devices it is possible to inadvertently insert the cannula and stylet while the cannula cutting tip is distally of the stylet tip and this would result in damage to body tissue due to coring.